Pump for implantable medical devices

ABSTRACT

A bidirectional electroosmotic pump may be provided. The bidirectional electroosmotic pump may be made of materials that are biocompatible and non-ferrous. The bidirectional electroosmotic pump may be part of an implantable medical device for the purpose of medicine delivery. The bidirectional electroosmotic pump may contain a working fluid and may facilitate the delivery of a separate payload fluid. In an exemplary embodiment, the bidirectional pump may contain bellows which may allow the pump to deliver the payload fluid through a series of valves and/or catheters. In another embodiment the bidirectional electroosmotic pump may contain a pump sensing mechanism to monitor the state of the pump.

BACKGROUND

The use of implantable drug delivery devices has reduced required and/orrepetitive surgeries, successfully targeted specific areas of the body,thereby increasing drug safety and efficacy, and eased the process ofproviding lifesaving medicine that was ineffective when deliveredsystemically; such as when surgical cancer resection is deemedimpossible, suboptimal, and/or less effective, like with chronic diseasemanagement and/or when systemic/oral medicine dosing is ineffective incrossing a homeostatic cellular barrier (e.g. blood brain barrier) andreaching the targeted organ or tissue (e.g. brain). A key benefit ofthese implantable devices is the ability to precisely control andmonitor how much of a medicine is being introduced to a specific bodypart and/or targeted organ. As a result, there is a serious concern andcritical need to ensure that implantable drug delivery devices maintaina consistent dosage during delivery and that over/under delivery ofmedicine is avoided; since the goal is to optimize target organ deliverywhile minimizing or avoiding altogether toxicity risks and collateraldamage to accessory, non-targeted organs. As such, the biocompatiblepumps contained within these implanted devices play an important role inreliably delivering medicine in instances when other delivery routessuch as oral or intravenous delivery are ineffective.

Currently, some implantable pumps used for patient disease managementfail to provide a consistent and appropriate dosage under variousenvironmental conditions, such as when the pump is within or near amagnetic resonance imaging (MRI) machine (e.g. they suffer loss of safeand dependable function after being within an MRI environment), withwhich the pumps are incompatible and unsafe. In other medicinal pumps,the internal components can react harshly with the medicine, resultingin serious malfunctions (e.g. viscosity issues leading to valveclogging), while other pump designs can mechanically fail over timegiven, for example, the repetitive movements required (e.g. peristalticpump mechanisms with ball bearings). Furthermore, some medicinal pumpscan have high power requirements that require large batteries and limitfunctional life (i.e. necessitating a repeat surgery every 3-7 years),while others cause visible deformity when placed in-situ under one'sskin and soft tissue given their poor shape and design incompatible withthe time-tested, methodical principles and practice of NeuroplasticSurgery (e.g. having sharp, firm, metal angles which cause unsafepressure points underneath the skin leading to pain and focal ischemia).Because most implantable pumps on the market today contain some form offerrous material, they cannot be effectively used in MRI settings. Theseissues can result in premature pump failure (e.g. metal corrosion),image distortion resulting in poor diagnostic information (i.e. failingto be MRI-lucent), poor patient satisfaction (e.g. by inhibiting apatient from entering a MRI machine, which can severely limit thediagnostic capabilities available for definitive treatment decisions),impaired quality of life (e.g. by preventing MRI-treatment proceduresfor pain relief, which can be combined with MRI imaging), prematureremoval of the pump halting delivery altogether (e.g. when prematuremechanical failure can only be addressed with additional surgery),and/or patient death if high concentrations of medicine are deliveredunexpectedly all at once above the therapeutic range (e.g. documentedcases of peristaltic pumps having overdosage post-MRI thereby leading tosevere consequences and major risk related to patient safety).

Implantable medical devices designed to deliver medicine to the body arecommonly large metallic objects that contain ferrous material. Thesedevices use conventional pumps, such as syringe pump mechanisms orperistaltic pump mechanisms which rely on bulky, ferrous, andpower-hungry motors. Electroosmosis is a commonly used mechanism inscientific research for microfluidic delivery of precise and low flowrates. There are very few commercially available electroosmotic pumps(EOPs), and only for direct transfer, or delivery, of a working fluid(WF) in a unidirectional flow pattern, thereby limiting their use anddelivery options to a limited set of liquids.

SUMMARY

According to at least one exemplary embodiment, an electroosmotic pumpmay be provided. The electroosmotic pump may be made of a variety ofmaterials that are biocompatible and non-ferrous. The electroosmoticpump may be part of an implantable medical device. The electroosmoticpump may contain a chamber that contains a working fluid. Theelectroosmotic pump may be designed to provide bidirectional flow topermit pumping a payload fluid which is different than the workingfluid. In an exemplary embodiment, the pump may contain bellows whichmay allow the pump to deliver the payload fluid through a series ofvalves and/or catheters. These bellows may be made of, for example,titanium (or other inert, durable material). In another embodiment theelectroosmotic pump may contain a pump sensing system to monitor thestate of the pump.

According to at least one exemplary embodiment, a method of using anelectroosmotic pump may be provided. The method of using theelectroosmotic pump may include moving a working fluid back and forthbetween an electroosmotic element housing and a bellows assembly byapplying alternating polarity electric potential to an electroosmoticelement through one or more electrodes. The reciprocating movement ofthe working fluid may drive two or more independent bellows which maydispense a payload fluid from the electroosmotic pump. Thisreciprocating movement may provide bidirectional flow and opposingvectors of medicinal catheter flow. Having at least two catheters perEOP, instead of one catheter per EOP, may add an additional layer ofduplicity which is invaluable when delivering medicine; given that onecatheter could become obstructed unexpectedly in the setting ofphysiological scar tissue development towards the end of one of thecatheters. This may allow for continued delivery of medicine withoutinterruption and may also shrink the potential footprint.

BRIEF DESCRIPTION OF THE FIGURES

Advantages of embodiments of the present invention will be apparent fromthe following detailed description of the exemplary embodiments. Thefollowing detailed description should be considered in conjunction withthe accompanying figures in which:

FIG. 1A shows a first exemplary embodiment of an electroosmotic pumpthat is designed with bi-directional flow that can minimize both theoverall footprint of a device as well as the area required within thehuman body for implantation.

FIG. 1B shows a cross-sectional view of an exemplary embodiment of abidirectional electroosmotic pump.

FIG. 1C shows a cross-sectional view of an exemplary embodiment of theparts of the bidirectional electroosmotic pump.

FIG. 2A shows an exemplary embodiment of an inner assembly of a pump.

FIG. 2B shows a cross-sectional view of an exemplary embodiment of theinner assembly of the pump.

FIG. 3 shows a cross-sectional view of an exemplary embodiment of thebidirectional electroosmotic pump highlighting the working fluid.

FIG. 4 shows a cross-sectional view of an exemplary embodiment of thebidirectional electroosmotic pump highlighting the payload fluid.

FIG. 5 shows an exemplary embodiment of an implant device embedded withthe bidirectional electroosmotic pump(s).

FIG. 6 shows a cross-section of an exemplary embodiment of aphoto-sensing mechanism.

FIG. 7A shown an exemplary alternative embodiment of a bidirectionalelectroosmotic pump.

FIG. 7B shows a cross-sectional view of the exemplary alternativeembodiment of the bidirectional electroosmotic pump.

FIG. 7C shows an exemplary inner assembly for the exemplary alternativeembodiment of the bidirectional electroosmotic pump.

FIG. 7D shows a cross sectional view of the exemplary inner assembly forthe exemplary alternative embodiment of the bidirectional electroosmoticpump.

FIG. 7E shows a cross sectional view of an exemplary bellows assemblyfor the exemplary alternative embodiment of the bidirectionalelectroosmotic pump.

FIG. 7F shows another cross sectional view of an exemplary bellowsassembly for the exemplary alternative embodiment of the bidirectionalelectroosmotic pump.

FIG. 7G shows an exemplary bidirectional electroosmotic pump assemblywith check valves.

FIG. 8 shows an exemplary method for using a bidirectionalelectroosmotic pump assembly.

DETAILED DESCRIPTION

Aspects of the invention are disclosed in the following description andrelated drawings directed to specific embodiments of the invention.Those skilled in the art will recognize that alternate embodiments maybe devised without departing from the spirit or the scope of the claims.Additionally, well-known elements of exemplary embodiments of theinvention will not be described in detail or will be omitted so as notto obscure the relevant details of the invention. Further, to facilitatean understanding of the description discussion of several terms usedherein follows.

As used herein, the word “exemplary” means “serving as an example,instance or illustration.” The embodiments described herein are notlimiting, but rather are exemplary only. It should be understood thatthe described embodiments are not necessarily to be construed aspreferred or advantageous over other embodiments. Moreover, the terms“embodiments of the invention”, “embodiments” or “invention” do notrequire that all embodiments of the invention include the discussedfeature, advantage or mode of operation.

As used herein, electroosmotic element (EOE) means a structure that hasa working fluid move through when a voltage is applied across thestructure. Because the fluid moves towards the negative terminal, byalternating the polarity of the applied voltage the electroosmoticelement can create reciprocating fluid motion.

As used herein, a bidirectional electroosmotic pump (EOP) means astructure that uses an EOE with an alternating polarity to drive apayload fluid, at a precise and low flowrate, in two directions.

FIG. 1A depicts an embodiment of an electroosmotic pump device 100 withan external housing 102 surrounding an inner assembly 104. It may beappreciated that the internal elements may be formed out of any of avariety of materials or combinations thereof, based on implementationand use. Further, in the embodiments, the components utilized in thepump assembly may be biocompatible with the human body and may be absentof any ferrous-containing elements, which can mitigate adverse effectsrelated to MRI equipment or imaging conditions and allow the device tobe both MRI-compatible and devoid of any radiological artifact. Thus, insome further embodiments, the embodiments may include a pump, or pumps,that are MRI-safe (i.e. the device, when used in the MRI environment,presents no additional risk to the patient or other individual, but itmay affect the quality of the diagnostic information), MRI-compatible(i.e. a device that is MRI safe when used in the MRI environment, toneither significantly affect the quality of the diagnostic informationnor have its operations affected by the MRI system), and/or MRI-lucent(i.e., a device that is MRI compatible and when used in the MRIenvironment, is radiographically invisible on MR imaging and therebyable to prevent unwanted artifact and prevent the risk of suboptimal MRimaging value for pathology assessment). The external housing 102 may becylindrical or, in other embodiments, adjusted to a different shapewhich is lower profile for human body implantation to avoid any visibledeformity when placed under skin and soft tissue. The external housing102 of the device may be formed from a biocompatible and durable plasticor photocured resin or any other safe and sterilizable material that isFDA-approved for reconstructive purposes. For example, the externalhousing 102 may be formed from any alloplastic material or paramagneticmaterial (i.e. titanium) capable of human use and compatible with theworking fluid and payload fluid. Other shapes and/or materials may beused based on the use and implementation of the pump for certain diseaseconditions and anatomical variance (i.e. placement within head, chest,abdomen, joint space, and/or extremity, as desired). Each end of theexternal housing 102 may include one or more valves 118 to facilitatethe flow of a payload fluid 120 without backflow. The one or more valves118 may be, for example, duckbill valves, and may be formed fromsilicone, Viton, fluorosilicone, or another MRI-lucent material. In anexemplary embodiment, the valves 118 may be duckbill valves, which maysupport an effective low flow rate system because of the small amount ofpressure required to open them and the lack of resistance created by thevalves 118. Other types of valve systems may include, but are notlimited to, diaphragm valves, custom valve flaps, umbrella valves, orother flow metering systems, as desired. In an exemplary embodiment,there may be a set of four valves, two of which facilitate the flow offluid into the pump and two of which facilitate driving fluid out of thepump. In other embodiments, there may be fewer valves utilized, whichmay be accomplished, for example, by combining fluid channels so thereis one inlet and one outlet valve. It may be understood that in otherembodiments, only two valves may be used, or more or less than fourvalves may be used, depending on application. In an embodiment, abi-directional pump may be desired over a uni-directional pump, becausethe bi-directionality may enable the delivery of a payload fluid, suchas, for example, a medicine to be directly delivered to the brain ortargeted body part, that is different than the working fluid within theEOP. Further, the added duplicity of two catheters per pump (versus onecatheter per pump) may mitigate instances of unexpected catheterblockage secondary to normal physiologic scar tissue followingplacement, which may be a safer and more effective option for chronicmedicine delivery.

FIG. 1B depicts an embodiment of the cross-sectional view of the deviceinner assembly 104 with parts of the inner assembly shown. In anembodiment, the inner assembly 104 may contain the electroosmoticelement 106 which may be contained by a holder 112 and may receive avoltage from electrodes 108. The holder 112 can be connected to bellows110 which can contain a working fluid 114. External to, or surrounding,the inner assembly 104 there may be the payload fluid 120 which may becontained by the external housing 102. It should be understood that thisis merely an exemplary configuration and, depending on application orlocation of an implant, different configurations may be used. Inaddition, the bellows can be shaped and designed with various forms toimprove long-term conditions, enhance function, and/or minimize wear,tear, or degradation.

FIG. 1C depicts a cross section of an embodiment of the electroosmoticpump device 100, with internal elements of the bidirectional pump shown.It may be appreciated that the internal elements may be formed out ofany of a variety of materials or combinations thereof, based onimplementation and use. In an embodiment, the electroosmotic device 100may include an electroosmotic element 106 that may be formed by, forexample, using a ceramic cylinder, or another porous material, and whichmay be contained by a holder 112, which may be formed, for example, withhigh-density polyethylene (HDPE), polyphenylene sulfide, polycarbonate,photocuring resin, or another material or set of materials that can bondaround the external surface of the electroosmotic element. In anexemplary embodiment, a ceramic element may be incorporated to avoid anyferrous materials and to assure MRI compatibility and/or MRI lucency.This may allow the pump(s) and/or any implanted devices using thepump(s) to increase long-term patient safety and enhance pumpfunctionality, for example with respect to MR imaging conditions,especially in instances where the patient's disease, like chronic brainor spine diseases, requires serial MR imaging. The electroosmoticelement 106 may be porous, which may enable the working fluid to flowthrough, causing the electroosmotic effect that drives the bidirectionalelectroosmotic pump.

Still referring to FIG. 1C, on either side of the electroosmotic pump100 may be electrodes 108, which may be formed of platinum or anotherconductive material in order to produce a voltage differential to movethe working fluid through the electroosmotic element. Platinum, in anembodiment, may be utilized for favorable material properties withrespect to, for example, ductility and chemical inertness. In anembodiment, platinum may be utilized because it can interact withvarious working fluids while remaining inert. Further, the platinum maybe formed into a desirable shape while maintaining electrical contactwith the electroosmotic element 106. Other, non-platinum, materials maydevelop an oxidation layer when an electrical charge is applied therebyreducing the conductivity of the material and resulting bidirectionalelectroosmotic pump performance. The electrodes 108 may deliver avoltage to the electroosmotic element 106 that can cause pumpingactuation to occur. The electroosmotic element holder 112 may beconnected to each bellows 110, which may be positioned on either side ofthe holder 112, and which may be capped by plugs 122. The bellows 110may be formed from titanium, silicone, fluoroelastomers, or otherelastic materials such as latex that are compatible with the workingfluid and the plugs 122 may be formed from resin, as desired. Thebellows 110 shape in the embodiments may be such that it may minimizesize, maximize function, and/or reduce long-term degradation associatedwith frequent or repetitive movements or from long-term contact with theworking fluid and payload fluid as may be required in use in someembodiments. The plug can be made from resin printing, silicone,plastics, or another material which may reliably bind to the bellows110. The plugs 122 can also be drilled so as to allow for filling withthe working fluid 114, and then may be resealed with additional resinand UV curing. The bellows 110 may contain a working fluid 114 which mayfacilitate the deformation of the bellows 110. This working fluid 114,in an exemplary embodiment, may be strategically chosen based on itssafety profile, polarity, it being a dielectric (which means apolarizable insulator), compatibility with the surrounding materials,such as the bellows, EOE, and holder, and/or its stability over timewith respect to bubble formation, and may be, but is not limited to,ethanol, DI water, or dimethyl sulfoxide (DMSO). In other embodimentsthe working fluid 114 may be another polar fluid compatible with thepump materials, and some embodiments may require the working fluid 114to be particle free, as particles in the working fluid 114 may clog thepores in the EOE, which may prevent the movement of the working fluid114, which may reduce flow rate or cease pumping entirely. In someembodiments the fluid may have a viscosity similar to water, and thefluid may be sterilized with a method compatible with the bidirectionalpump. For example, with ethylene oxide sterilization. Surrounding theholder 112 and the bellows 110 may be a casing 116 (for example formedof resin) that can contain an inner assembly 104 and the payload fluid120. On each end of the casing 116 there may be two valves 118, forexample formed of silicone, which can facilitate flow of the payloadfluid 120 in and out of the electroosmotic pump 100.

FIG. 2A depicts an exemplary embodiment of the inner assembly 204. Itmay be appreciated that the parts may be formed out of any of a varietyof biocompatible materials or combinations thereof for human bodyimplantation, based on implementation and desired use, and/or forimplantation in various animals. In this embodiment, the bellows 210 mayextend from either end of the holder 212 and can be capped 222 toprevent the working fluid 214 from escaping. In this embodiment, theelastic design of the bellows 210 may facilitate their expansion andcontraction in a precise manner so as to prevent over or under deliveryof medicine, which could result in impaired patient safety, adverse drugevents, and/or patient death. For example, the bidirectional pump mayfacilitate a flow rate of 0.5-5 μl/min, which may be desirable forspecific applications including convection-enhanced delivery (CED). Itmay be appreciated that another configuration of the bellows 210 andtheir plugs may be used, depending on the implementation or packaging ofthe implant. Furthermore, in an embodiment, a sensor located inside ofthe implant may be utilized to provide, for example, an embeddedbiosensing system and/or data as to when the bellows 210 are in use oroperation, maximally/partially flex and maximally/partially unflex, andalso to alert a patient and/or healthcare provider of improper pumpfunction with enhanced safety alarms. In other embodiments, customrubber domes may replace the bellows 210 and plugs. In such anembodiment, the state of the pumping cycle can be detected using, forexample, IR LEDs and phototransistors to determine the extent ofdeformation or expansion. Based on the reading, the pump can alternateflow direction. Another alternative embodiment may include customconductive rubber domes which can be formed into various shapes. Theconductive diaphragms may come into contact with the electrodes 208 andsend signals to alternate the polarity. Further alternate embodimentscould include latex coated in graphene, or a fluid barrier where a fluidmembrane is used instead of a physical piece. This fluid membrane couldbe, for example, air in a microfluidic channel, a liquid metal, oil, orother fluid that may not mix with either the working or payload fluid.

FIG. 2B depicts an embodiment of a cross-sectional view of the innerassembly 204. The electroosmotic element 206 may be supported by theholder 212, and electrodes 208 may be on either side of theelectroosmotic element 206 and extend out of the inner assembly 204. Theelectrodes 208 may extend to receive a voltage and deliver it to theelectroosmotic element 206. In this embodiment, the working fluid 214may be enclosed within the bellows 210 to drive their movement. In somefurther embodiments, a sealant may further be utilized with the pump(s)or an implant associated therewith to further ensure that the workingfluid 214 does not leak out and/or mix with any of the medical contentsbeing pumped in to the human body or critical organ. In an exemplaryembodiment the sealant may be a material unaffected by the chemicalproperties of the working fluid 214.

FIG. 3 depicts a cross-section view of an embodiment of a bidirectionalelectroosmotic pump 300. It may be appreciated that the elements may beformed out of any of a variety of biocompatible materials orcombinations thereof, based on implementation and use within, forexample, the human body. In this figure, the working fluid 314 isdisplayed with cross-hatching. The working fluid 314 may include avariety of fluids based on electrical conduction properties andlong-term ability to prevent bubble formation secondary to molecularelectrolysis and/or repetitive conduction. Types of working fluids 314may depend on the ability to be moved by electroosmosis and couldinclude, for example deionized water, ethanol, or DMSO. In otherembodiments the working fluid 314 may be another polar fluid compatiblewith the pump materials that may be used, and in some embodimentscompatibility may require the working fluid 314 to be particle free, asparticles in the working fluid 314 may clog the pores in the EOE, whichmay prevent the movement of the working fluid, which may reduce flowrate or cease pumping entirely 314. In some embodiments the fluid mayhave a viscosity similar to water, and the fluid may be sterilized witha method compatible with the pump. For example, with ethylene oxidesterilization. The working fluid 314 may surround the electroosmoticelement 306 and the electrodes 308. The working fluid 314,electroosmotic element 306 and electrodes 308 may all be confined withinthe holder 312 and be capped 322.

FIG. 4 depicts a cross-sectional view of an embodiment of abidirectional electroosmotic pump 400. It may be appreciated that theparts may be formed out of any of a variety of biocompatible materialsor combinations thereof, based on implementation and use. In thisfigure, the payload fluid 420 is displayed with cross-hatching.Possibilities for the payload fluid 420 may include a specific fluidwhich is time-stable and able to not degrade and remain at constantvolume without evaporating or electrolyzing over time at normothermicconditions (for example, 98.6 degrees Fahrenheit). The payload fluid 420may be able to flow through sub 1.5 mm channels and may include anywater-based fluid or fluid with similar properties. The payload fluid420 may be stable at human body temperature, have low viscosity, becompatible with any material used in the system, and/or be injectablethrough a device refill system. The payload fluid 420 may surround theinner assembly 404 and itself can be enclosed by the external housing416. A series of valves 418 may facilitate the flow of the payload fluid420 in and out of the pump 400. In an embodiment, the external housing416 may include four valves 418, two of which may direct the payloadfluid 420 outward, two which may bring the payload fluid 420 in. It maybe understood that other embodiments may utilize different numbers ofvalves and/or orientations of the valves. For example, in otherembodiments, only two valves may be used, or more than four plugs may beused. Further, it may be appreciated that valves 418 may provide for anadditional level of safety for and control of drug delivery in instanceswhere too little or too much drug delivery can cause severe adverseevents including brain injury, spinal cord paralysis, tumor recurrence,and/or patient death. Thus, in such embodiments, valves 418 may bemonitored by some associated sensors and/or controlled such as toprevent any over- or under-delivery of medicine.

FIG. 5 depicts an embodiment of an implant device 500 that can be usedto deliver medicine. It may be appreciated that the elements may beformed out of any of a variety of biocompatible materials orcombinations thereof, based on implementation and use. In thisembodiment, the device may contain two bidirectional pumps 524 inparallel connected to four exit catheters 526 which may extend out ofthe device. The pump arrangement can be reconfigured based on the devicedesign and goals; and may contain a varying number of pumps and exitport catheters based on clinical application and/or final sizerequirements. Further, in the embodiment of FIG. 5 , the arrangement ofthe bidirectional pumps 524 may provide for maximized multi-catheterpump flow and minimized overall footprint, thereby improving patientoutcomes when implanted in the human body. Further, such an arrangementof pumps 524 may also mitigate risks for visible deformity statuspost-operatively (i.e. a visible pump on a person's head when receivingbrain medicine through a pump delivery system). The pumps may beconfigured in a way to transmit fluid from the device. The catheters 526may be formed by a flexible, biocompatible material to carry fluid fromthe device and to the target area. The catheters may be able to, forexample, allow for 0.5-5 μl/min of fluid to pass through them. It may beunderstood that the number and type of the exit port can be adjustedbased on need. Having multiple catheters may be advantageous oversinge-catheter devices in that there is additional duplicity of medicinedelivery in case a catheter blockage was to occur (i.e., with a onecatheter device system a blockage formation equates to no medicinedelivery versus a two catheter device system which may still continue todeliver medicine).

In an exemplary embodiment the device may also include a battery. Thebattery may be ideal when deemed MRI compatible in line with the rest ofthe device. In the embodiments, any battery or battery system may have afixed life span, or, have a rechargeable battery system which may usewireless charging. The pump may be powered by, for example, any batterywith a long enough life span, or a wirelessly rechargeable power source,both of which may deliver power to the system and contain minimalferromagnetic materials.

In an alternative embodiment, a photo-sensing system may be analternative method of sensing the state of the pump. The photo-sensingsystem may use infrared (IR) LEDs and phototransistors to sense thestate of a membrane separating the working and payload fluids. Analternative shape may be utilized, for example a shape consisting of adome made from silicone or other elastic material. The bidirectionalpump may be able to utilize such an LED-phototransistor combination todetect how deformed or compressed the rubber dome is at any point intime and therefore detect the status of the pump's pumping cycle. Forexample, if the elastic dome is extended towards the EOE, thephototransistor may receive less IR light from the LED. Vice versa, whenthe dome is completely collapsed, the phototransistor may receive moreIR light from the LED.

FIG. 6 depicts a cross-section of an exemplary embodiment of aphoto-sensing mechanism 600. The photo-sensing mechanism 600 may have anIR LED 602 which transmits light across the diameter of the pumpassembly. Further, there may be a platinum wire 604 which provides abarrier for the light to pass through to fully close the light sensingcircuit. The photo-sensing mechanism 600 may also have an IRphototransistor 606 that detects deformation of a rubber dome 608. Therubber dome 608 may be dipped in another material, for example graphene,on the internal and/or external faces. In other embodiments the dome 608may instead be made of fluorinated carbon-based synthetic rubber (FKM),fluorosilicone, or any other elastic material. The rubber dome 608 maybe able to be deformed at the tip and collapse into itself. This motionmay allow for an optical path between the LED 602 and thephototransistor 606. By determining whether the path exists or isblocked the state of the bellows may be determined.

In other embodiments, as an alternative to using solid material toseparate the working and payload fluids, a fluid membrane may be used.The fluid membrane may be, for example, a liquid metal, oil, or anyother fluid that will not be absorbed into the working or payload fluid.This fluid membrane may achieve the same interaction as a solid barrierprovided by a metal bellow or rubber dome. The fluid membrane may bemoved, therefore moving the payload fluid, by, for example, beingoscillated by the working fluid movement through the electroosmoticelement (EOE). Oscillations of the fluid membrane may be achieved in away that prevents any form of negative auditory feedback to the patientfollowing human body implantation. This may be critical, for example, inembodiments where the implantable bidirectional pump sits within askull-soft tissue temporal space in close proximity to the patient'sear.

In an exemplary embodiment the components may be bonded together using aone-part, biocompatible, room temperature vulcanizing (RTV) silicone. Inother embodiments, the components may be bonded using, for example butnot limited to, laser welding, spot welding, glass-metal seals,ultrasonic welding, epoxies, or UV adhesives.

In an exemplary embodiment, the bidirectional electroosmotic pump(s) maybe integrated into a medical implant case. The case may be designed tomatch the human body shape constraints (i.e. using well acceptednormative data) related to its final anatomical destination; so that itcan be provided to the physician/surgeon as an “off-the-shelf” solution.This may also allow for outlet pathways to exit ports for the payloadfluid to also be embedded into the medical implant case. The pump(s) maybe connected by, for example, manifolds, silicone tubing, and/or fittingpieces.

FIG. 7A depicts an exemplary alternative embodiment of a bidirectionalelectroosmotic pump. The exemplary EOP 700 design may have one or moreelectrodes 702 that may power the EOP 700. The one or more electrodes702 may be made of, for example, platinum. The EOP 700 may further havean EOP bellows housing 704 which may further have an outer housing 706and an inner housing 708. The bellow housing 704, outer housing 706, andinner housing 708 may be made of, for example, titanium, another metal,polyphenylene sulfide (PPS), other plastics, other polymers, and/or anyother materials known in the art. In some embodiments the outer housing706 and the inner housing 708 may be made of the same material while inothers they may be made of different material. The inner housing 708 andouter housing 706 may be connected through, for example, welding,ultrasonic welding, or an adhesive. The EOP 700 may further have an EOEhousing 710. The EOE housing 710 may be connected to the bellows housing704 by a connector 712. The EOE housing 710 may be made of, for example,polymers, titanium, another metal, glass, and/or ceramics. A workingfluid 764 may further be contained in the EOE housing 710. It may beunderstood that the working fluid may be able to move between the EOEhousing 710 and the EOP bellows housing 704 via the connector 712. TheEOP 700 may further be connected to a pump management printed circuitboard (PCB) 714 which may be connected to and control the electrodes 702and/or to bellows sensing wires 726.

FIG. 7B depicts a cross-sectional view 720 of the exemplary alternativeembodiment of the EOP 700. Within the EOE housing 710 there may be anelectroosmotic element 722. The electrodes 702 may be attached to theelectroosmotic element through, for example, insert molding to passelectric charge to the electroosmotic element face, which may be, forexample, platinum paste. The electroosmotic element 722 may be amaterial such as ceramic, that when voltage is applied to theelectroosmotic element 722 through the electrodes 702 the working fluid764 is moved. The electroosmotic element 722 may be porous, which mayenable the working fluid to flow through, causing the electroosmoticeffect that drives the bidirectional electroosmotic pump. In anexemplary embodiment, the electroosmotic element 722 may be, forexample, a porous ceramic body. In other embodiments, the electroosmoticelement 722 may be other materials, including but not limited to variousdielectrics such as sintered glass, silica, and/or alumina. When thevoltage being applied to the electrodes 702 is alternated between afirst polarity and a second opposite polarity, a reciprocating fluidmotion may be generated through the movement of the working fluid 764.This movement may help control movement of bellows 724, for example bymoving via the connector 712 into one or more working fluid chambers728. The bellows 724 may be, for example, a titanium foil that is formedinto a dome shape and deforms under pressure. The bellows 724 may beconnected to the EOP bellows housing via, for example, welding. Themovement of the bellows 724 may be detected and recorded by one or morebellows sensors 726 which may be contained within one or more of theworking fluid chambers 728 and/or payload fluid chambers 730. Thebellows sensors 726 may be attached using, for example, epoxy. Thebellows sensors 726 may be electrodes and may work by, for example,sensing an electrical connection created when the bellows 724 deform andcontact the bellows sensors 726. When the bellows sensors 726 sense sucha connection or otherwise determine that the bellows have been deformed,the electrodes 702 may switch polarity to the opposite polarity, whichmay begin a new pumping cycle.

FIGS. 7C and 7D depict an exemplary inner assembly 740 of theelectroosmotic element housing 710 for the exemplary alternativeembodiment of the bidirectional electroosmotic pump 700.

FIGS. 7E and 7F depict an interior view of the exemplary alternativeembodiment of the bidirectional electroosmotic pump 760. Initially, thepayload chamber 730 may be filled with a payload fluid 762, where thepayload fluid 762 may be, for example, saline, an MRI tracer such asgadolinium, a medication such as topotecan, another medication known tobe a safe and effective anti-tumor medicine in the setting of high gradeglioma, or another fluid with clinical benefits known in the art. Insome embodiments, the payload fluid may be a combination of fluids, forexample, an MRI tracer and a medication, or two or more medications,where the fluids are compatible with each other. As electroosmosis isused to move the working fluid 764, the one or more working fluidchambers 728 may be filled, causing the bellows in the payload chamber730 to restrict and expand, thereby pushing some of the payload fluid762 out to be delivered.

FIG. 7G depicts an EOP assembly utilizing the exemplary alternativeembodiment of the EOP 780. The EOP 700 may be connected with one or morecheck valves 782 via one or more joints 784. The one or more joints 784may facilitate movement of the payload fluid 762 to the check valves782. In an exemplary embodiment, as the reciprocating motion of thebellows intakes the payload fluid 762, the check valves 782 may allowfluid to pass through from the reservoir and the outlet valves may helpprevent backflow. Backflow would be dangerous in instances of medicinereflux, and therefore, may be avoided using a valve-assisted design suchas this. When the bellows 724 expel the payload fluid 762 the inletvalve may prevent backflow while the outlet valve dispenses the payloadfluid 762, for example, through one or more catheters.

FIG. 8 depicts an exemplary method for using a bidirectionalelectroosmotic pump 800. For the sake of example, the method will beshown with reference to the bidirectional electroosmotic pump 700described in FIGS. 7A-7G, however, in other embodiments the method 800may be used with other electroosmotic pumps such as those describedabove, or other embodiments not described herein. In a first step 802,the working fluid 764 may be moved from the electroosmotic elementhousing 710 to the bellows assembly 704 by applying a first polarityelectric potential to the one or more electrodes 702. This may cause thebellows 742 to deform as the working fluid 764 begins to fill the one ormore working fluid chambers 728. In a second step 804 the deformation ofthe bellows 742 may be sensed by the one or more bellows sensors 726 andcommunicated to other systems via the pump management PCB 714.

In a third step 806 the working fluid 764 may be moved back to theelectroosmotic housing 710 from the bellows assembly 704 by switchingthe polarity of the electric potential being applied to the one or moreelectrodes 702 to the opposite polarity. The switch may be doneautomatically based on the sensing mechanism described in step 804. In afourth step 808, steps 802-806 may be repeated periodically in order tocreate a reciprocating movement of the working fluid 764, which mayallow the bellows 742 to move at a continuous rate. The periodic ratemay be based on the sensing mechanism, and the sensing mechanism mayhave a programmable delay to control the switching time span. In a finalstep 810, the payload fluid 762 may be dispensed from the bidirectionalelectroosmotic pump based on the movement of the bellows. By using anembedded software technology platform, the time interval of each sensingmechanism and pump adjustment may be adjusted wirelessly and remotely atany timepoint; thereby changing hourly, daily, weekly, monthly, and/oryearly quantities of medicine delivery through different instantaneousactive flow rates, average flow rates based on swept volume, and/orinfusion schedules. In an exemplary embodiment the pump may have amirrored design which causes the sides of the pump to alternate whichstep of FIG. 8 they are on. For example, if the first pump is on step802 the second half of the pump may simultaneously be on step 806.

The foregoing description and accompanying figures illustrate theprinciples, preferred embodiments and modes of operation of theinvention. However, the invention should not be construed as beinglimited to the particular embodiments discussed above. Additionalvariations of the embodiments discussed above will be appreciated bythose skilled in the art. Additionally it may be understood that partsor aspects described in one embodiment may likewise be used in otherembodiments where appropriate.

Therefore, the above-described embodiments should be regarded asillustrative rather than restrictive. Accordingly, it should beappreciated that variations to those embodiments can be made by thoseskilled in the art without departing from the scope of the invention asdefined by the following claims.

What is claimed is:
 1. A bidirectional pump for medical implants, comprising: an electroosmotic element housing comprising: an electroosmotic element; and one or more electrodes which pass through the electroosmotic element; a bellows assembly comprising: a bellows housing; two or more bellows within the bellows housing; one or more bellows sensors within the bellows housing; and a payload fluid which can be dispensed based on movement of the two or more bellows; and a connector which allows for movement of a working fluid from the electroosmotic element housing to the bellows assembly and back from the bellows assembly to the electroosmotic element housing based on an electrical current being applied to the one or more electrodes.
 2. The pump of claim 1, wherein the bellows housing further comprises: an inner housing; an outer housing; one or more working fluid chambers, which can hold the working fluid; and one or more payload fluid chambers, which can hold the payload fluid.
 3. The pump of claim 2, wherein the two or more bellows are situated in the one or more working fluid chambers and/or the one or more payload fluid chambers, and the two or more bellows are made of titanium foil.
 4. The pump of claim 3, further comprising a pump management PCB that is connected to both the electroosmotic element housing and the bellows assembly; wherein the pump management PCB detects a pumping cycle through the one or more bellows sensors.
 5. The pump of claim 1, wherein the bellows housing is made of one of titanium, polyethylene terephthalate (PET), or polyphenylene sulfide.
 6. The pump of claim 1, further comprising: one or more check valves; and one or more joints connecting the one or more check valves to the bellows assembly.
 7. The pump of claim 1, wherein the electroosmotic element is made of one or more of ceramic and platinum.
 8. The pump of claim 7, wherein the electroosmotic element is a porous ceramic body with porous platinum paste applied to two faces of the ceramic body; the one or more electrodes are attached to the electroosmotic element through insert molding; and electric current is passed to the electroosmotic element from the one or more electrodes through the porous platinum paste.
 9. The pump of claim 1, wherein the working fluid is a particle free polar fluid with viscosity of about that of water.
 10. The pump of claim 1, wherein the payload fluid is one or more of saline, an MRI tracer, and a fluid with clinical benefits.
 11. A method for delivering fluid through an implanted medical device, comprising: moving a working fluid from an electroosmotic element housing to a bellows assembly by applying a first polarity electric current to an electroosmotic element through one or more electrodes which pass through the electroosmotic element; sensing deformation of a bellows caused by the movement of the working fluid from the electroosmotic element housing to the bellows assembly via one or more bellows sensors within a bellows housing contained in the bellows assembly; moving the working fluid from the bellows assembly to the electroosmotic element housing by applying an opposite polarity electric current to the one or more electrodes after detecting the deformation of the bellows; moving the working fluid in a reciprocating fluid fashion by periodically repeating the applying of the first polarity electric current and the opposite polarity electric current to the one or more electrodes; and dispensing a payload fluid by the deformation of the bellows caused by the reciprocating fluid motion of the working fluid.
 12. The method of claim 11, wherein the bellows housing further comprises: an inner housing; an outer housing; one or more working fluid chambers configured to hold the working fluid; and one or more payload fluid chambers configured to hold the payload fluid.
 13. The method of claim 12, wherein the bellows are situated in the one or more working fluid chambers and/or the one or more payload fluid chambers, and the bellows is formed from titanium foil.
 14. The method of claim 13, further comprising communicating information from the bellows sensors to a pump management PCB that is connected to both the electroosmotic element housing and the bellows assembly.
 15. The method of claim 11, wherein the bellows housing is made of one of titanium, polyethylene terephthalate (PET), or polyphenylene sulfide.
 16. The method of claim 11, wherein the electroosmotic element is one of ceramic or platinum.
 17. The method of claim 16, wherein the electroosmotic element is a porous ceramic body with porous platinum paste applied to two faces of the ceramic body; the one or more electrodes are attached to the electroosmotic element through insert molding; and electric current is passed to the electroosmotic element from the one or more electrodes through the porous platinum paste.
 18. The method of claim 11, wherein the working fluid is a particle free polar fluid with viscosity of about that of water.
 19. The method of claim 11, wherein the payload fluid is one or more of saline, an MRI tracer, and a fluid with clinical benefits. 